Momentary forces on a structure can induce dynamic responses into the structure, including vibrations, which can weaken the structure, subject its occupants to the unpleasantness or hazards associated with this vibratory motion, and adversely impact the performance of equipment located within the structure. Accordingly, solutions to damp these dynamic responses in structures have been sought.
For example, Japanese Patent Applications 62-328916 and 61-12569 describe damping systems having springs and dashpots suspending a secondary mass or weight from a primary mass. Japanese Patent Application 62-328916 describes a weight connected to a floor by two springs and two dashpots, for damping oscillations in the floor. Japanese Patent Application 61-12569 describes a tuned damping system where the mass of the weight, and the spring constant of the spring element are chosen such that the frequency of the system is tuned to the natural frequency of the floor or ceiling element to be damped. This tuning enhances the damping ability of the system.
Kim and Yeo, "Application of Viscoelastic Material for a Dynamic Damper" in Journal of Vibration, Acoustics, Stress, and Reliability in Design, Vol. 108 (July 1986) pp. 378-381, reported that some damping systems employed springs, or springs in conjunction with friction or fluid dashpots, to suspend a damper mass from a primary mass. Their paper describes a viscoelastic material under prestrain used in conjunction with a damper mass as a system for replacing the spring and dashpot damping systems.
Halverson and Hansen, "Use of Rubber Materials in Tuned Dampers for Vibration and Noise Control", in Rubbercon '88, describes a tuned damping system using a rubber material as the spring and damping elements between a mass element and a base structure.
Viscoelastic materials are also used in structural damping applications. For example, U.S. Pat. No. 3,605,953 to Caldwell et al., Mahmoodi, "Structural Dampers" in Journal of the Structural Division, Proceedings of the American Society of Civil Engineers, 1661 (August 1969), and Keel and Mahmoodi, "Design of Viscoelastic Dampers for Columbia Center Building," in Building Motion in Wind, Proceedings of a session sponsored by the Aerodynamics Committee of the Aerospace Division and the Wind Effects Committee of the Structural Division of the American Society of Civil Engineers in conjunction with the ASCE convention in Seattle, Wash., Apr. 8, 1986, describe dampers, which show layers of metal plates having viscoelastic material between the plates. The viscoelastic material of the dampers transfers a portion of the vibratory energy of the structure into heat, which is subsequently dissipated into the surroundings.